/**
 * @author Rich Tibbett / https://github.com/richtr
 * @author mrdoob / http://mrdoob.com/
 * @author Tony Parisi / http://www.tonyparisi.com/
 * @author Takahiro / https://github.com/takahirox
 * @author Don McCurdy / https://www.donmccurdy.com
 */
/*
 * 本文档为Three.js翻译文档，如有任何疑问请联系:
 * dreameng1997@163.com
 */
THREE.GLTFLoader = (function () {

    /**
     * @description GLTF的加载文件
     * @date 2019-04-16
     * @param {*} manager 加载管理器
     */
    function GLTFLoader(manager) {
        //新建一个加载管理器
        this.manager = (manager !== undefined) ? manager : THREE.DefaultLoadingManager;
        //设置点云加载器为空，接收draco文件的
        this.dracoLoader = null;
    }

    GLTFLoader.prototype = {

        constructor: GLTFLoader,

        crossOrigin: 'anonymous',
        /**
         * @description gltf加载方法
         * @date 2019-04-17
         * @param {*} url url的地址
         * @param {*} onLoad	加载方法
         * @param {*} onProgress	加载过程中调用的方法
         * @param {*} onError	加载失败调用的方法
         */
        load: function (url, onLoad, onProgress, onError) {
            //获得this
            var scope = this;
            //创建一个资源路径
            var resourcePath;
            //获得路径
            if (this.resourcePath !== undefined) {

                resourcePath = this.resourcePath;

            } else if (this.path !== undefined) {

                resourcePath = this.path;

            } else {

                resourcePath = THREE.LoaderUtils.extractUrlBase(url);

            }

            // Tells the LoadingManager to track an extra item, which resolves after
            // the model is fully loaded. This means the count of items loaded will
            // be incorrect, but ensures manager.onLoad() does not fire early.
            //加载管理器开始监听url
            scope.manager.itemStart(url);
            //加载失败的方法
            var _onError = function (e) {

                if (onError) {

                    onError(e);

                } else {

                    console.error(e);

                }

                scope.manager.itemError(url);
                scope.manager.itemEnd(url);

            };
            //新建一个文件加载器
            var loader = new THREE.FileLoader(scope.manager);
            //设置路径
            loader.setPath(this.path);
            //设置响应类型，响应类型在FileLoader有写
            loader.setResponseType('arraybuffer');
            //开始加载资源，有两个参数，一个是url一个是加载成功的数据方法
            loader.load(url, function (data) {

                try {
                    //尝试去加载资源
                    scope.parse(data, resourcePath, function (gltf) {
                        //返回的gltf是可以直接导入到场景的gltf
                        onLoad(gltf);
                        //结束管理器的监听
                        scope.manager.itemEnd(url);

                    }, _onError);

                } catch (e) {

                    _onError(e);

                }

            }, onProgress, _onError);

        },

        /**
         * @description 应该是设置gltf的类型
         * @date 2019-04-17
         * @param {*} value
         * @returns
         */
        setCrossOrigin: function (value) {

            this.crossOrigin = value;
            return this;

        },

        /**
         * @description 设置路径
         * @date 2019-04-17
         * @param {*} value
         * @returns
         */
        setPath: function (value) {

            this.path = value;
            return this;

        },

        /**
         * @description 设置资源路径,这个和上一个的区别是上一个可以是一个相对路径，这个是绝对路径
         * @date 2019-04-17
         * @param {*} value
         * @returns
         */
        setResourcePath: function (value) {

            this.resourcePath = value;
            return this;

        },

        /**
         * @description 设置DRACO文件的加载器
         * @date 2019-04-17
         * @param {*} dracoLoader
         * @returns
         */
        setDRACOLoader: function (dracoLoader) {

            this.dracoLoader = dracoLoader;
            return this;

        },

        /**
         * @description 加载成功的分析方法
         * @date 2019-04-17
         * @param {*} data 加载出来的数据，对于模型来说，一般为arrayBuffer类型的
         * @param {*} path 加载路径
         * @param {*} onLoad	加载成功方法
         * @param {*} onError	加载失败方法
         * @returns
         */
        parse: function (data, path, onLoad, onError) {
            //新建内容变量和拓展变量数组
            var content;
            var extensions = {};
            //判断data类型如果是string类型的直接赋值
            if (typeof data === 'string') {

                content = data;

            } else {
                //如果不是string类型，首先取出前四个判断是不是:"{"
                var magic = THREE.LoaderUtils.decodeText(new Uint8Array(data, 0, 4));
                //如果前四个是gltf，应该是glb格式的二进制文件，获得具体的数据
                if (magic === BINARY_EXTENSION_HEADER_MAGIC) {

                    try {

                        extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(data);

                    } catch (error) {

                        if (onError) onError(error);
                        return;

                    }

                    content = extensions[EXTENSIONS.KHR_BINARY_GLTF].content;

                } else {
                    //如果是正常的gltf就转换类型
                    content = THREE.LoaderUtils.decodeText(new Uint8Array(data));

                }

            }
            //转换为json格式
            var json = JSON.parse(content);
            //各个gltf不一样，以下的格式加载就不属于模型的范畴了，加载的东西也是千奇百怪，不具体翻译了，可以对照THREE的gltf对照的看
            if (json.asset === undefined || json.asset.version[0] < 2) {

                if (onError) onError(new Error('THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported. Use LegacyGLTFLoader instead.'));
                return;

            }

            if (json.extensionsUsed) {

                for (var i = 0; i < json.extensionsUsed.length; ++i) {

                    var extensionName = json.extensionsUsed[i];
                    var extensionsRequired = json.extensionsRequired || [];

                    switch (extensionName) {

                        case EXTENSIONS.KHR_LIGHTS_PUNCTUAL:
                            extensions[extensionName] = new GLTFLightsExtension(json);
                            break;

                        case EXTENSIONS.KHR_MATERIALS_UNLIT:
                            extensions[extensionName] = new GLTFMaterialsUnlitExtension(json);
                            break;

                        case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
                            extensions[extensionName] = new GLTFMaterialsPbrSpecularGlossinessExtension(json);
                            break;

                        case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
                            extensions[extensionName] = new GLTFDracoMeshCompressionExtension(json, this.dracoLoader);
                            break;

                        case EXTENSIONS.MSFT_TEXTURE_DDS:
                            extensions[EXTENSIONS.MSFT_TEXTURE_DDS] = new GLTFTextureDDSExtension();
                            break;

                        case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
                            extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] = new GLTFTextureTransformExtension(json);
                            break;

                        default:

                            if (extensionsRequired.indexOf(extensionName) >= 0) {

                                console.warn('THREE.GLTFLoader: Unknown extension "' + extensionName + '".');

                            }

                    }

                }

            }

            var parser = new GLTFParser(json, extensions, {

                path: path || this.resourcePath || '',
                crossOrigin: this.crossOrigin,
                manager: this.manager

            });

            parser.parse(function (scene, scenes, cameras, animations, json) {

                var glTF = {
                    scene: scene,
                    scenes: scenes,
                    cameras: cameras,
                    animations: animations,
                    asset: json.asset,
                    parser: parser,
                    userData: {}
                };

                addUnknownExtensionsToUserData(extensions, glTF, json);

                onLoad(glTF);

            }, onError);

        }

    };

    /* GLTFREGISTRY */

    /**
     * @description 创建一个在缓存中的注册函数
     * @date 2019-04-17
     * @returns
     */
    function GLTFRegistry() {

        var objects = {};

        return {

            get: function (key) {

                return objects[key];

            },

            add: function (key, object) {

                objects[key] = object;

            },

            remove: function (key) {

                delete objects[key];

            },

            removeAll: function () {

                objects = {};

            }

        };

    }

    /*********************************/
    /********** EXTENSIONS ***********/
    /*********************************/

    var EXTENSIONS = {
        KHR_BINARY_GLTF: 'KHR_binary_glTF',
        KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
        KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
        KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
        KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
        KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
        MSFT_TEXTURE_DDS: 'MSFT_texture_dds'
    };


    /**
     * DDS Texture Extension
     *
     * Specification:
     * https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
     *
     */
    /**
     * @description dds图片的拓展
     * @date 2019-04-17
     */
    function GLTFTextureDDSExtension() {

        if (!THREE.DDSLoader) {

            throw new Error('THREE.GLTFLoader: Attempting to load .dds texture without importing THREE.DDSLoader');

        }

        this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
        this.ddsLoader = new THREE.DDSLoader();

    }

    /**
     * Lights Extension
     *
     * Specification: PENDING
     */
    /**
     * @description 灯光的拓展，及获取
     * @date 2019-04-17
     * @param {*} json
     */
    function GLTFLightsExtension(json) {

        this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

        var extension = (json.extensions && json.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]) || {};
        this.lightDefs = extension.lights || [];

    }
    /**
     * @description 加载灯光
     * @date 2019-04-17
     * @param {*} lightIndex 灯光的下标
     */
    GLTFLightsExtension.prototype.loadLight = function (lightIndex) {

        var lightDef = this.lightDefs[lightIndex];
        var lightNode;

        var color = new THREE.Color(0xffffff);
        if (lightDef.color !== undefined) color.fromArray(lightDef.color);

        var range = lightDef.range !== undefined ? lightDef.range : 0;

        switch (lightDef.type) {

            case 'directional':
                lightNode = new THREE.DirectionalLight(color);
                lightNode.target.position.set(0, 0, -1);
                lightNode.add(lightNode.target);
                break;

            case 'point':
                lightNode = new THREE.PointLight(color);
                lightNode.distance = range;
                break;

            case 'spot':
                lightNode = new THREE.SpotLight(color);
                lightNode.distance = range;
                // Handle spotlight properties.
                lightDef.spot = lightDef.spot || {};
                lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
                lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
                lightNode.angle = lightDef.spot.outerConeAngle;
                lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
                lightNode.target.position.set(0, 0, -1);
                lightNode.add(lightNode.target);
                break;

            default:
                throw new Error('THREE.GLTFLoader: Unexpected light type, "' + lightDef.type + '".');

        }

        // Some lights (e.g. spot) default to a position other than the origin. Reset the position
        // here, because node-level parsing will only override position if explicitly specified.
        lightNode.position.set(0, 0, 0);

        lightNode.decay = 2;

        if (lightDef.intensity !== undefined) lightNode.intensity = lightDef.intensity;

        lightNode.name = lightDef.name || ('light_' + lightIndex);

        return Promise.resolve(lightNode);

    };

    /**
     * Unlit Materials Extension (pending)
     *
     * PR: https://github.com/KhronosGroup/glTF/pull/1163
     */
    function GLTFMaterialsUnlitExtension(json) {

        this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;

    }

    GLTFMaterialsUnlitExtension.prototype.getMaterialType = function (material) {

        return THREE.MeshBasicMaterial;

    };

    GLTFMaterialsUnlitExtension.prototype.extendParams = function (materialParams, material, parser) {

        var pending = [];

        materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
        materialParams.opacity = 1.0;

        var metallicRoughness = material.pbrMetallicRoughness;

        if (metallicRoughness) {

            if (Array.isArray(metallicRoughness.baseColorFactor)) {

                var array = metallicRoughness.baseColorFactor;

                materialParams.color.fromArray(array);
                materialParams.opacity = array[3];

            }

            if (metallicRoughness.baseColorTexture !== undefined) {

                pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));

            }

        }

        return Promise.all(pending);

    };

    /* BINARY EXTENSION */

    var BINARY_EXTENSION_BUFFER_NAME = 'binary_glTF';
    var BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
    var BINARY_EXTENSION_HEADER_LENGTH = 12;
    var BINARY_EXTENSION_CHUNK_TYPES = {
        JSON: 0x4E4F534A,
        BIN: 0x004E4942
    };

    /**
     * @description 加载二进制gltf格式的文件
     * @date 2019-04-17
     * @param {*} data 获得到数据
     */
    function GLTFBinaryExtension(data) {
        //设置名字为gltf二进制文件
        this.name = EXTENSIONS.KHR_BINARY_GLTF;
        //创建内容
        this.content = null;
        //
        this.body = null;
        //获得首视图，获得前12个字符组成的类型视图。
        var headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH);
        //获得头标识，不同的gltf会有不同的处理这里以three的为例
        this.header = {
            magic: THREE.LoaderUtils.decodeText(new Uint8Array(data.slice(0, 4))),
            version: headerView.getUint32(4, true),
            length: headerView.getUint32(8, true)
        };

        if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {

            throw new Error('THREE.GLTFLoader: Unsupported glTF-Binary header.');

        } else if (this.header.version < 2.0) {

            throw new Error('THREE.GLTFLoader: Legacy binary file detected. Use LegacyGLTFLoader instead.');

        }
        //这块每个gltf都不太一样，不具体翻译了
        var chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH);
        var chunkIndex = 0;
        //取数据
        while (chunkIndex < chunkView.byteLength) {

            var chunkLength = chunkView.getUint32(chunkIndex, true);
            chunkIndex += 4;

            var chunkType = chunkView.getUint32(chunkIndex, true);
            chunkIndex += 4;

            if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {

                var contentArray = new Uint8Array(data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength);
                this.content = THREE.LoaderUtils.decodeText(contentArray);

            } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {

                var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
                this.body = data.slice(byteOffset, byteOffset + chunkLength);

            }

            // Clients must ignore chunks with unknown types.

            chunkIndex += chunkLength;

        }

        if (this.content === null) {

            throw new Error('THREE.GLTFLoader: JSON content not found.');

        }

    }

    /**
     * DRACO Mesh Compression Extension
     *
     * Specification: https://github.com/KhronosGroup/glTF/pull/874
     */
    function GLTFDracoMeshCompressionExtension(json, dracoLoader) {

        if (!dracoLoader) {

            throw new Error('THREE.GLTFLoader: No DRACOLoader instance provided.');

        }

        this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
        this.json = json;
        this.dracoLoader = dracoLoader;
        THREE.DRACOLoader.getDecoderModule();

    }

    GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function (primitive, parser) {

        var json = this.json;
        var dracoLoader = this.dracoLoader;
        var bufferViewIndex = primitive.extensions[this.name].bufferView;
        var gltfAttributeMap = primitive.extensions[this.name].attributes;
        var threeAttributeMap = {};
        var attributeNormalizedMap = {};
        var attributeTypeMap = {};

        for (var attributeName in gltfAttributeMap) {

            if (!(attributeName in ATTRIBUTES)) continue;

            threeAttributeMap[ATTRIBUTES[attributeName]] = gltfAttributeMap[attributeName];

        }

        for (attributeName in primitive.attributes) {

            if (ATTRIBUTES[attributeName] !== undefined && gltfAttributeMap[attributeName] !== undefined) {

                var accessorDef = json.accessors[primitive.attributes[attributeName]];
                var componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

                attributeTypeMap[ATTRIBUTES[attributeName]] = componentType;
                attributeNormalizedMap[ATTRIBUTES[attributeName]] = accessorDef.normalized === true;

            }

        }

        return parser.getDependency('bufferView', bufferViewIndex).then(function (bufferView) {

            return new Promise(function (resolve) {

                dracoLoader.decodeDracoFile(bufferView, function (geometry) {

                    for (var attributeName in geometry.attributes) {

                        var attribute = geometry.attributes[attributeName];
                        var normalized = attributeNormalizedMap[attributeName];

                        if (normalized !== undefined) attribute.normalized = normalized;

                    }

                    resolve(geometry);

                }, threeAttributeMap, attributeTypeMap);

            });

        });

    };

    /**
     * Texture Transform Extension
     *
     * Specification:
     */
    function GLTFTextureTransformExtension(json) {

        this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;

    }

    GLTFTextureTransformExtension.prototype.extendTexture = function (texture, transform) {

        texture = texture.clone();

        if (transform.offset !== undefined) {

            texture.offset.fromArray(transform.offset);

        }

        if (transform.rotation !== undefined) {

            texture.rotation = transform.rotation;

        }

        if (transform.scale !== undefined) {

            texture.repeat.fromArray(transform.scale);

        }

        if (transform.texCoord !== undefined) {

            console.warn('THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.');

        }

        texture.needsUpdate = true;

        return texture;

    };

    /**
     * Specular-Glossiness Extension
     *
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
     */
    /**
     * @description 拓展材质的shader啥的
     * @date 2019-04-17
     * @returns
     */
    function GLTFMaterialsPbrSpecularGlossinessExtension() {

        return {

            name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,

            specularGlossinessParams: [
                'color',
                'map',
                'lightMap',
                'lightMapIntensity',
                'aoMap',
                'aoMapIntensity',
                'emissive',
                'emissiveIntensity',
                'emissiveMap',
                'bumpMap',
                'bumpScale',
                'normalMap',
                'displacementMap',
                'displacementScale',
                'displacementBias',
                'specularMap',
                'specular',
                'glossinessMap',
                'glossiness',
                'alphaMap',
                'envMap',
                'envMapIntensity',
                'refractionRatio',
            ],

            getMaterialType: function () {

                return THREE.ShaderMaterial;

            },

            extendParams: function (params, material, parser) {

                var pbrSpecularGlossiness = material.extensions[this.name];

                var shader = THREE.ShaderLib['standard'];

                var uniforms = THREE.UniformsUtils.clone(shader.uniforms);

                var specularMapParsFragmentChunk = [
                    '#ifdef USE_SPECULARMAP',
                    '	uniform sampler2D specularMap;',
                    '#endif'
                ].join('\n');

                var glossinessMapParsFragmentChunk = [
                    '#ifdef USE_GLOSSINESSMAP',
                    '	uniform sampler2D glossinessMap;',
                    '#endif'
                ].join('\n');

                var specularMapFragmentChunk = [
                    'vec3 specularFactor = specular;',
                    '#ifdef USE_SPECULARMAP',
                    '	vec4 texelSpecular = texture2D( specularMap, vUv );',
                    '	texelSpecular = sRGBToLinear( texelSpecular );',
                    '	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
                    '	specularFactor *= texelSpecular.rgb;',
                    '#endif'
                ].join('\n');

                var glossinessMapFragmentChunk = [
                    'float glossinessFactor = glossiness;',
                    '#ifdef USE_GLOSSINESSMAP',
                    '	vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
                    '	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
                    '	glossinessFactor *= texelGlossiness.a;',
                    '#endif'
                ].join('\n');

                var lightPhysicalFragmentChunk = [
                    'PhysicalMaterial material;',
                    'material.diffuseColor = diffuseColor.rgb;',
                    'material.specularRoughness = clamp( 1.0 - glossinessFactor, 0.04, 1.0 );',
                    'material.specularColor = specularFactor.rgb;',
                ].join('\n');

                var fragmentShader = shader.fragmentShader
                    .replace('uniform float roughness;', 'uniform vec3 specular;')
                    .replace('uniform float metalness;', 'uniform float glossiness;')
                    .replace('#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk)
                    .replace('#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk)
                    .replace('#include <roughnessmap_fragment>', specularMapFragmentChunk)
                    .replace('#include <metalnessmap_fragment>', glossinessMapFragmentChunk)
                    .replace('#include <lights_physical_fragment>', lightPhysicalFragmentChunk);

                delete uniforms.roughness;
                delete uniforms.metalness;
                delete uniforms.roughnessMap;
                delete uniforms.metalnessMap;

                uniforms.specular = {
                    value: new THREE.Color().setHex(0x111111)
                };
                uniforms.glossiness = {
                    value: 0.5
                };
                uniforms.specularMap = {
                    value: null
                };
                uniforms.glossinessMap = {
                    value: null
                };

                params.vertexShader = shader.vertexShader;
                params.fragmentShader = fragmentShader;
                params.uniforms = uniforms;
                params.defines = {
                    'STANDARD': ''
                };

                params.color = new THREE.Color(1.0, 1.0, 1.0);
                params.opacity = 1.0;

                var pending = [];

                if (Array.isArray(pbrSpecularGlossiness.diffuseFactor)) {

                    var array = pbrSpecularGlossiness.diffuseFactor;

                    params.color.fromArray(array);
                    params.opacity = array[3];

                }

                if (pbrSpecularGlossiness.diffuseTexture !== undefined) {

                    pending.push(parser.assignTexture(params, 'map', pbrSpecularGlossiness.diffuseTexture));

                }

                params.emissive = new THREE.Color(0.0, 0.0, 0.0);
                params.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
                params.specular = new THREE.Color(1.0, 1.0, 1.0);

                if (Array.isArray(pbrSpecularGlossiness.specularFactor)) {

                    params.specular.fromArray(pbrSpecularGlossiness.specularFactor);

                }

                if (pbrSpecularGlossiness.specularGlossinessTexture !== undefined) {

                    var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
                    pending.push(parser.assignTexture(params, 'glossinessMap', specGlossMapDef));
                    pending.push(parser.assignTexture(params, 'specularMap', specGlossMapDef));

                }

                return Promise.all(pending);

            },

            createMaterial: function (params) {

                // setup material properties based on MeshStandardMaterial for Specular-Glossiness

                var material = new THREE.ShaderMaterial({
                    defines: params.defines,
                    vertexShader: params.vertexShader,
                    fragmentShader: params.fragmentShader,
                    uniforms: params.uniforms,
                    fog: true,
                    lights: true,
                    opacity: params.opacity,
                    transparent: params.transparent
                });

                material.isGLTFSpecularGlossinessMaterial = true;

                material.color = params.color;

                material.map = params.map === undefined ? null : params.map;

                material.lightMap = null;
                material.lightMapIntensity = 1.0;

                material.aoMap = params.aoMap === undefined ? null : params.aoMap;
                material.aoMapIntensity = 1.0;

                material.emissive = params.emissive;
                material.emissiveIntensity = 1.0;
                material.emissiveMap = params.emissiveMap === undefined ? null : params.emissiveMap;

                material.bumpMap = params.bumpMap === undefined ? null : params.bumpMap;
                material.bumpScale = 1;

                material.normalMap = params.normalMap === undefined ? null : params.normalMap;
                if (params.normalScale) material.normalScale = params.normalScale;

                material.displacementMap = null;
                material.displacementScale = 1;
                material.displacementBias = 0;

                material.specularMap = params.specularMap === undefined ? null : params.specularMap;
                material.specular = params.specular;

                material.glossinessMap = params.glossinessMap === undefined ? null : params.glossinessMap;
                material.glossiness = params.glossiness;

                material.alphaMap = null;

                material.envMap = params.envMap === undefined ? null : params.envMap;
                material.envMapIntensity = 1.0;

                material.refractionRatio = 0.98;

                material.extensions.derivatives = true;

                return material;

            },

            /**
             * Clones a GLTFSpecularGlossinessMaterial instance. The ShaderMaterial.copy() method can
             * copy only properties it knows about or inherits, and misses many properties that would
             * normally be defined by MeshStandardMaterial.
             *
             * This method allows GLTFSpecularGlossinessMaterials to be cloned in the process of
             * loading a glTF model, but cloning later (e.g. by the user) would require these changes
             * AND also updating `.onBeforeRender` on the parent mesh.
             *
             * @param  {THREE.ShaderMaterial} source
             * @return {THREE.ShaderMaterial}
             */
            cloneMaterial: function (source) {

                var target = source.clone();

                target.isGLTFSpecularGlossinessMaterial = true;

                var params = this.specularGlossinessParams;

                for (var i = 0, il = params.length; i < il; i++) {

                    target[params[i]] = source[params[i]];

                }

                return target;

            },

            // Here's based on refreshUniformsCommon() and refreshUniformsStandard() in WebGLRenderer.
            refreshUniforms: function (renderer, scene, camera, geometry, material, group) {

                if (material.isGLTFSpecularGlossinessMaterial !== true) {

                    return;

                }

                var uniforms = material.uniforms;
                var defines = material.defines;

                uniforms.opacity.value = material.opacity;

                uniforms.diffuse.value.copy(material.color);
                uniforms.emissive.value.copy(material.emissive).multiplyScalar(material.emissiveIntensity);

                uniforms.map.value = material.map;
                uniforms.specularMap.value = material.specularMap;
                uniforms.alphaMap.value = material.alphaMap;

                uniforms.lightMap.value = material.lightMap;
                uniforms.lightMapIntensity.value = material.lightMapIntensity;

                uniforms.aoMap.value = material.aoMap;
                uniforms.aoMapIntensity.value = material.aoMapIntensity;

                // uv repeat and offset setting priorities
                // 1. color map
                // 2. specular map
                // 3. normal map
                // 4. bump map
                // 5. alpha map
                // 6. emissive map

                var uvScaleMap;

                if (material.map) {

                    uvScaleMap = material.map;

                } else if (material.specularMap) {

                    uvScaleMap = material.specularMap;

                } else if (material.displacementMap) {

                    uvScaleMap = material.displacementMap;

                } else if (material.normalMap) {

                    uvScaleMap = material.normalMap;

                } else if (material.bumpMap) {

                    uvScaleMap = material.bumpMap;

                } else if (material.glossinessMap) {

                    uvScaleMap = material.glossinessMap;

                } else if (material.alphaMap) {

                    uvScaleMap = material.alphaMap;

                } else if (material.emissiveMap) {

                    uvScaleMap = material.emissiveMap;

                }

                if (uvScaleMap !== undefined) {

                    // backwards compatibility
                    if (uvScaleMap.isWebGLRenderTarget) {

                        uvScaleMap = uvScaleMap.texture;

                    }

                    if (uvScaleMap.matrixAutoUpdate === true) {

                        uvScaleMap.updateMatrix();

                    }

                    uniforms.uvTransform.value.copy(uvScaleMap.matrix);

                }

                if (material.envMap) {

                    uniforms.envMap.value = material.envMap;
                    uniforms.envMapIntensity.value = material.envMapIntensity;

                    // don't flip CubeTexture envMaps, flip everything else:
                    //  WebGLRenderTargetCube will be flipped for backwards compatibility
                    //  WebGLRenderTargetCube.texture will be flipped because it's a Texture and NOT a CubeTexture
                    // this check must be handled differently, or removed entirely, if WebGLRenderTargetCube uses a CubeTexture in the future
                    uniforms.flipEnvMap.value = material.envMap.isCubeTexture ? -1 : 1;

                    uniforms.reflectivity.value = material.reflectivity;
                    uniforms.refractionRatio.value = material.refractionRatio;

                    uniforms.maxMipLevel.value = renderer.properties.get(material.envMap).__maxMipLevel;

                }

                uniforms.specular.value.copy(material.specular);
                uniforms.glossiness.value = material.glossiness;

                uniforms.glossinessMap.value = material.glossinessMap;

                uniforms.emissiveMap.value = material.emissiveMap;
                uniforms.bumpMap.value = material.bumpMap;
                uniforms.normalMap.value = material.normalMap;

                uniforms.displacementMap.value = material.displacementMap;
                uniforms.displacementScale.value = material.displacementScale;
                uniforms.displacementBias.value = material.displacementBias;

                if (uniforms.glossinessMap.value !== null && defines.USE_GLOSSINESSMAP === undefined) {

                    defines.USE_GLOSSINESSMAP = '';
                    // set USE_ROUGHNESSMAP to enable vUv
                    defines.USE_ROUGHNESSMAP = '';

                }

                if (uniforms.glossinessMap.value === null && defines.USE_GLOSSINESSMAP !== undefined) {

                    delete defines.USE_GLOSSINESSMAP;
                    delete defines.USE_ROUGHNESSMAP;

                }

            }

        };

    }

    /*********************************/
    /********** INTERPOLATION ********/
    /*********************************/

    // Spline Interpolation
    // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
    function GLTFCubicSplineInterpolant(parameterPositions, sampleValues, sampleSize, resultBuffer) {

        THREE.Interpolant.call(this, parameterPositions, sampleValues, sampleSize, resultBuffer);

    }

    GLTFCubicSplineInterpolant.prototype = Object.create(THREE.Interpolant.prototype);
    GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;

    GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function (index) {

        // Copies a sample value to the result buffer. See description of glTF
        // CUBICSPLINE values layout in interpolate_() function below.

        var result = this.resultBuffer,
            values = this.sampleValues,
            valueSize = this.valueSize,
            offset = index * valueSize * 3 + valueSize;

        for (var i = 0; i !== valueSize; i++) {

            result[i] = values[offset + i];

        }

        return result;

    };

    GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

    GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

    GLTFCubicSplineInterpolant.prototype.interpolate_ = function (i1, t0, t, t1) {

        var result = this.resultBuffer;
        var values = this.sampleValues;
        var stride = this.valueSize;

        var stride2 = stride * 2;
        var stride3 = stride * 3;

        var td = t1 - t0;

        var p = (t - t0) / td;
        var pp = p * p;
        var ppp = pp * p;

        var offset1 = i1 * stride3;
        var offset0 = offset1 - stride3;

        var s2 = -2 * ppp + 3 * pp;
        var s3 = ppp - pp;
        var s0 = 1 - s2;
        var s1 = s3 - pp + p;

        // Layout of keyframe output values for CUBICSPLINE animations:
        //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
        for (var i = 0; i !== stride; i++) {

            var p0 = values[offset0 + i + stride]; // splineVertex_k
            var m0 = values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
            var p1 = values[offset1 + i + stride]; // splineVertex_k+1
            var m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)

            result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;

        }

        return result;

    };

    /*********************************/
    /********** INTERNALS ************/
    /*********************************/

    /* CONSTANTS */

    var WEBGL_CONSTANTS = {
        FLOAT: 5126,
        //FLOAT_MAT2: 35674,
        FLOAT_MAT3: 35675,
        FLOAT_MAT4: 35676,
        FLOAT_VEC2: 35664,
        FLOAT_VEC3: 35665,
        FLOAT_VEC4: 35666,
        LINEAR: 9729,
        REPEAT: 10497,
        SAMPLER_2D: 35678,
        POINTS: 0,
        LINES: 1,
        LINE_LOOP: 2,
        LINE_STRIP: 3,
        TRIANGLES: 4,
        TRIANGLE_STRIP: 5,
        TRIANGLE_FAN: 6,
        UNSIGNED_BYTE: 5121,
        UNSIGNED_SHORT: 5123
    };

    var WEBGL_TYPE = {
        5126: Number,
        //35674: THREE.Matrix2,
        35675: THREE.Matrix3,
        35676: THREE.Matrix4,
        35664: THREE.Vector2,
        35665: THREE.Vector3,
        35666: THREE.Vector4,
        35678: THREE.Texture
    };

    var WEBGL_COMPONENT_TYPES = {
        5120: Int8Array,
        5121: Uint8Array,
        5122: Int16Array,
        5123: Uint16Array,
        5125: Uint32Array,
        5126: Float32Array
    };

    var WEBGL_FILTERS = {
        9728: THREE.NearestFilter,
        9729: THREE.LinearFilter,
        9984: THREE.NearestMipMapNearestFilter,
        9985: THREE.LinearMipMapNearestFilter,
        9986: THREE.NearestMipMapLinearFilter,
        9987: THREE.LinearMipMapLinearFilter
    };

    var WEBGL_WRAPPINGS = {
        33071: THREE.ClampToEdgeWrapping,
        33648: THREE.MirroredRepeatWrapping,
        10497: THREE.RepeatWrapping
    };

    var WEBGL_SIDES = {
        1028: THREE.BackSide, // Culling front
        1029: THREE.FrontSide // Culling back
        //1032: THREE.NoSide   // Culling front and back, what to do?
    };

    var WEBGL_DEPTH_FUNCS = {
        512: THREE.NeverDepth,
        513: THREE.LessDepth,
        514: THREE.EqualDepth,
        515: THREE.LessEqualDepth,
        516: THREE.GreaterEqualDepth,
        517: THREE.NotEqualDepth,
        518: THREE.GreaterEqualDepth,
        519: THREE.AlwaysDepth
    };

    var WEBGL_BLEND_EQUATIONS = {
        32774: THREE.AddEquation,
        32778: THREE.SubtractEquation,
        32779: THREE.ReverseSubtractEquation
    };

    var WEBGL_BLEND_FUNCS = {
        0: THREE.ZeroFactor,
        1: THREE.OneFactor,
        768: THREE.SrcColorFactor,
        769: THREE.OneMinusSrcColorFactor,
        770: THREE.SrcAlphaFactor,
        771: THREE.OneMinusSrcAlphaFactor,
        772: THREE.DstAlphaFactor,
        773: THREE.OneMinusDstAlphaFactor,
        774: THREE.DstColorFactor,
        775: THREE.OneMinusDstColorFactor,
        776: THREE.SrcAlphaSaturateFactor
        // The followings are not supported by Three.js yet
        //32769: CONSTANT_COLOR,
        //32770: ONE_MINUS_CONSTANT_COLOR,
        //32771: CONSTANT_ALPHA,
        //32772: ONE_MINUS_CONSTANT_COLOR
    };

    var WEBGL_TYPE_SIZES = {
        'SCALAR': 1,
        'VEC2': 2,
        'VEC3': 3,
        'VEC4': 4,
        'MAT2': 4,
        'MAT3': 9,
        'MAT4': 16
    };

    var ATTRIBUTES = {
        POSITION: 'position',
        NORMAL: 'normal',
        TANGENT: 'tangent',
        TEXCOORD_0: 'uv',
        TEXCOORD_1: 'uv2',
        COLOR_0: 'color',
        WEIGHTS_0: 'skinWeight',
        JOINTS_0: 'skinIndex',
    };

    var PATH_PROPERTIES = {
        scale: 'scale',
        translation: 'position',
        rotation: 'quaternion',
        weights: 'morphTargetInfluences'
    };

    var INTERPOLATION = {
        CUBICSPLINE: THREE.InterpolateSmooth, // We use custom interpolation GLTFCubicSplineInterpolation for CUBICSPLINE.
        // KeyframeTrack.optimize() can't handle glTF Cubic Spline output values layout,
        // using THREE.InterpolateSmooth for KeyframeTrack instantiation to prevent optimization.
        // See KeyframeTrack.optimize() for the detail.
        LINEAR: THREE.InterpolateLinear,
        STEP: THREE.InterpolateDiscrete
    };

    var STATES_ENABLES = {
        2884: 'CULL_FACE',
        2929: 'DEPTH_TEST',
        3042: 'BLEND',
        3089: 'SCISSOR_TEST',
        32823: 'POLYGON_OFFSET_FILL',
        32926: 'SAMPLE_ALPHA_TO_COVERAGE'
    };

    var ALPHA_MODES = {
        OPAQUE: 'OPAQUE',
        MASK: 'MASK',
        BLEND: 'BLEND'
    };

    var MIME_TYPE_FORMATS = {
        'image/png': THREE.RGBAFormat,
        'image/jpeg': THREE.RGBFormat
    };

    /* UTILITY FUNCTIONS */

    function resolveURL(url, path) {

        // Invalid URL
        if (typeof url !== 'string' || url === '') return '';

        // Absolute URL http://,https://,//
        if (/^(https?:)?\/\//i.test(url)) return url;

        // Data URI
        if (/^data:.*,.*$/i.test(url)) return url;

        // Blob URL
        if (/^blob:.*$/i.test(url)) return url;

        // Relative URL
        return path + url;

    }

    var defaultMaterial;

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
     */
    function createDefaultMaterial() {

        defaultMaterial = defaultMaterial || new THREE.MeshStandardMaterial({
            color: 0xFFFFFF,
            emissive: 0x000000,
            metalness: 1,
            roughness: 1,
            transparent: false,
            depthTest: true,
            side: THREE.FrontSide
        });

        return defaultMaterial;

    }

    function addUnknownExtensionsToUserData(knownExtensions, object, objectDef) {

        // Add unknown glTF extensions to an object's userData.

        for (var name in objectDef.extensions) {

            if (knownExtensions[name] === undefined) {

                object.userData.gltfExtensions = object.userData.gltfExtensions || {};
                object.userData.gltfExtensions[name] = objectDef.extensions[name];

            }

        }

    }

    /**
     * @param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
     * @param {GLTF.definition} gltfDef
     */
    function assignExtrasToUserData(object, gltfDef) {

        if (gltfDef.extras !== undefined) {

            if (typeof gltfDef.extras === 'object') {

                object.userData = gltfDef.extras;

            } else {

                console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras);

            }

        }

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
     *
     * @param {THREE.BufferGeometry} geometry
     * @param {Array<GLTF.Target>} targets
     * @param {GLTFParser} parser
     * @return {Promise<THREE.BufferGeometry>}
     */
    function addMorphTargets(geometry, targets, parser) {

        var hasMorphPosition = false;
        var hasMorphNormal = false;

        for (var i = 0, il = targets.length; i < il; i++) {

            var target = targets[i];

            if (target.POSITION !== undefined) hasMorphPosition = true;
            if (target.NORMAL !== undefined) hasMorphNormal = true;

            if (hasMorphPosition && hasMorphNormal) break;

        }

        if (!hasMorphPosition && !hasMorphNormal) return Promise.resolve(geometry);

        var pendingPositionAccessors = [];
        var pendingNormalAccessors = [];

        for (var i = 0, il = targets.length; i < il; i++) {

            var target = targets[i];

            if (hasMorphPosition) {

                // TODO: Error-prone use of a callback inside a loop.
                var accessor = target.POSITION !== undefined ?
                    parser.getDependency('accessor', target.POSITION)
                        .then(function (accessor) {

                            // Cloning not to pollute original accessor below
                            return cloneBufferAttribute(accessor);

                        }) :
                    geometry.attributes.position;

                pendingPositionAccessors.push(accessor);

            }

            if (hasMorphNormal) {

                // TODO: Error-prone use of a callback inside a loop.
                var accessor = target.NORMAL !== undefined ?
                    parser.getDependency('accessor', target.NORMAL)
                        .then(function (accessor) {

                            return cloneBufferAttribute(accessor);

                        }) :
                    geometry.attributes.normal;

                pendingNormalAccessors.push(accessor);

            }

        }

        return Promise.all([
            Promise.all(pendingPositionAccessors),
            Promise.all(pendingNormalAccessors)
        ]).then(function (accessors) {

            var morphPositions = accessors[0];
            var morphNormals = accessors[1];

            for (var i = 0, il = targets.length; i < il; i++) {

                var target = targets[i];
                var attributeName = 'morphTarget' + i;

                if (hasMorphPosition) {

                    // Three.js morph position is absolute value. The formula is
                    //   basePosition
                    //     + weight0 * ( morphPosition0 - basePosition )
                    //     + weight1 * ( morphPosition1 - basePosition )
                    //     ...
                    // while the glTF one is relative
                    //   basePosition
                    //     + weight0 * glTFmorphPosition0
                    //     + weight1 * glTFmorphPosition1
                    //     ...
                    // then we need to convert from relative to absolute here.

                    if (target.POSITION !== undefined) {

                        var positionAttribute = morphPositions[i];
                        positionAttribute.name = attributeName;

                        var position = geometry.attributes.position;

                        for (var j = 0, jl = positionAttribute.count; j < jl; j++) {

                            positionAttribute.setXYZ(
                                j,
                                positionAttribute.getX(j) + position.getX(j),
                                positionAttribute.getY(j) + position.getY(j),
                                positionAttribute.getZ(j) + position.getZ(j)
                            );

                        }

                    }

                }

                if (hasMorphNormal) {

                    // see target.POSITION's comment

                    if (target.NORMAL !== undefined) {

                        var normalAttribute = morphNormals[i];
                        normalAttribute.name = attributeName;

                        var normal = geometry.attributes.normal;

                        for (var j = 0, jl = normalAttribute.count; j < jl; j++) {

                            normalAttribute.setXYZ(
                                j,
                                normalAttribute.getX(j) + normal.getX(j),
                                normalAttribute.getY(j) + normal.getY(j),
                                normalAttribute.getZ(j) + normal.getZ(j)
                            );

                        }

                    }

                }

            }

            if (hasMorphPosition) geometry.morphAttributes.position = morphPositions;
            if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals;

            return geometry;

        });

    }

    /**
     * @param {THREE.Mesh} mesh
     * @param {GLTF.Mesh} meshDef
     */
    function updateMorphTargets(mesh, meshDef) {

        mesh.updateMorphTargets();

        if (meshDef.weights !== undefined) {

            for (var i = 0, il = meshDef.weights.length; i < il; i++) {

                mesh.morphTargetInfluences[i] = meshDef.weights[i];

            }

        }

        // .extras has user-defined data, so check that .extras.targetNames is an array.
        if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {

            var targetNames = meshDef.extras.targetNames;

            if (mesh.morphTargetInfluences.length === targetNames.length) {

                mesh.morphTargetDictionary = {};

                for (var i = 0, il = targetNames.length; i < il; i++) {

                    mesh.morphTargetDictionary[targetNames[i]] = i;

                }

            } else {

                console.warn('THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.');

            }

        }

    }

    function isObjectEqual(a, b) {

        if (Object.keys(a).length !== Object.keys(b).length) return false;

        for (var key in a) {

            if (a[key] !== b[key]) return false;

        }

        return true;

    }

    function createPrimitiveKey(primitiveDef) {

        var dracoExtension = primitiveDef.extensions && primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION];
        var geometryKey;

        if (dracoExtension) {

            geometryKey = 'draco:' + dracoExtension.bufferView +
                ':' + dracoExtension.indices +
                ':' + createAttributesKey(dracoExtension.attributes);

        } else {

            geometryKey = primitiveDef.indices + ':' + createAttributesKey(primitiveDef.attributes) + ':' + primitiveDef.mode;

        }

        return geometryKey;

    }

    function createAttributesKey(attributes) {

        var attributesKey = '';

        var keys = Object.keys(attributes).sort();

        for (var i = 0, il = keys.length; i < il; i++) {

            attributesKey += keys[i] + ':' + attributes[keys[i]] + ';';

        }

        return attributesKey;

    }

    function cloneBufferAttribute(attribute) {

        if (attribute.isInterleavedBufferAttribute) {

            var count = attribute.count;
            var itemSize = attribute.itemSize;
            var array = attribute.array.slice(0, count * itemSize);

            for (var i = 0, j = 0; i < count; ++i) {

                array[j++] = attribute.getX(i);
                if (itemSize >= 2) array[j++] = attribute.getY(i);
                if (itemSize >= 3) array[j++] = attribute.getZ(i);
                if (itemSize >= 4) array[j++] = attribute.getW(i);

            }

            return new THREE.BufferAttribute(array, itemSize, attribute.normalized);

        }

        return attribute.clone();

    }

    /* GLTF PARSER */

    function GLTFParser(json, extensions, options) {

        this.json = json || {};
        this.extensions = extensions || {};
        this.options = options || {};

        // loader object cache
        this.cache = new GLTFRegistry();

        // BufferGeometry caching
        this.primitiveCache = {};

        this.textureLoader = new THREE.TextureLoader(this.options.manager);
        this.textureLoader.setCrossOrigin(this.options.crossOrigin);

        this.fileLoader = new THREE.FileLoader(this.options.manager);
        this.fileLoader.setResponseType('arraybuffer');

    }

    GLTFParser.prototype.parse = function (onLoad, onError) {

        var json = this.json;

        // Clear the loader cache
        this.cache.removeAll();

        // Mark the special nodes/meshes in json for efficient parse
        this.markDefs();

        // Fire the callback on complete
        this.getMultiDependencies([

            'scene',
            'animation',
            'camera'

        ]).then(function (dependencies) {

            var scenes = dependencies.scenes || [];
            var scene = scenes[json.scene || 0];
            var animations = dependencies.animations || [];
            var cameras = dependencies.cameras || [];

            onLoad(scene, scenes, cameras, animations, json);

        }).catch(onError);

    };

    /**
     * Marks the special nodes/meshes in json for efficient parse.
     */
    GLTFParser.prototype.markDefs = function () {

        var nodeDefs = this.json.nodes || [];
        var skinDefs = this.json.skins || [];
        var meshDefs = this.json.meshes || [];

        var meshReferences = {};
        var meshUses = {};

        // Nothing in the node definition indicates whether it is a Bone or an
        // Object3D. Use the skins' joint references to mark bones.
        for (var skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex++) {

            var joints = skinDefs[skinIndex].joints;

            for (var i = 0, il = joints.length; i < il; i++) {

                nodeDefs[joints[i]].isBone = true;

            }

        }

        // Meshes can (and should) be reused by multiple nodes in a glTF asset. To
        // avoid having more than one THREE.Mesh with the same name, count
        // references and rename instances below.
        //
        // Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
        for (var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {

            var nodeDef = nodeDefs[nodeIndex];

            if (nodeDef.mesh !== undefined) {

                if (meshReferences[nodeDef.mesh] === undefined) {

                    meshReferences[nodeDef.mesh] = meshUses[nodeDef.mesh] = 0;

                }

                meshReferences[nodeDef.mesh]++;

                // Nothing in the mesh definition indicates whether it is
                // a SkinnedMesh or Mesh. Use the node's mesh reference
                // to mark SkinnedMesh if node has skin.
                if (nodeDef.skin !== undefined) {

                    meshDefs[nodeDef.mesh].isSkinnedMesh = true;

                }

            }

        }

        this.json.meshReferences = meshReferences;
        this.json.meshUses = meshUses;

    };

    /**
     * Requests the specified dependency asynchronously, with caching.
     * @param {string} type
     * @param {number} index
     * @return {Promise<THREE.Object3D|THREE.Material|THREE.Texture|THREE.AnimationClip|ArrayBuffer|Object>}
     */
    GLTFParser.prototype.getDependency = function (type, index) {

        var cacheKey = type + ':' + index;
        var dependency = this.cache.get(cacheKey);

        if (!dependency) {

            switch (type) {

                case 'scene':
                    dependency = this.loadScene(index);
                    break;

                case 'node':
                    dependency = this.loadNode(index);
                    break;

                case 'mesh':
                    dependency = this.loadMesh(index);
                    break;

                case 'accessor':
                    dependency = this.loadAccessor(index);
                    break;

                case 'bufferView':
                    dependency = this.loadBufferView(index);
                    break;

                case 'buffer':
                    dependency = this.loadBuffer(index);
                    break;

                case 'material':
                    dependency = this.loadMaterial(index);
                    break;

                case 'texture':
                    dependency = this.loadTexture(index);
                    break;

                case 'skin':
                    dependency = this.loadSkin(index);
                    break;

                case 'animation':
                    dependency = this.loadAnimation(index);
                    break;

                case 'camera':
                    dependency = this.loadCamera(index);
                    break;

                case 'light':
                    dependency = this.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].loadLight(index);
                    break;

                default:
                    throw new Error('Unknown type: ' + type);

            }

            this.cache.add(cacheKey, dependency);

        }

        return dependency;

    };

    /**
     * Requests all dependencies of the specified type asynchronously, with caching.
     * @param {string} type
     * @return {Promise<Array<Object>>}
     */
    GLTFParser.prototype.getDependencies = function (type) {

        var dependencies = this.cache.get(type);

        if (!dependencies) {

            var parser = this;
            var defs = this.json[type + (type === 'mesh' ? 'es' : 's')] || [];

            dependencies = Promise.all(defs.map(function (def, index) {

                return parser.getDependency(type, index);

            }));

            this.cache.add(type, dependencies);

        }

        return dependencies;

    };

    /**
     * Requests all multiple dependencies of the specified types asynchronously, with caching.
     * @param {Array<string>} types
     * @return {Promise<Object<Array<Object>>>}
     */
    GLTFParser.prototype.getMultiDependencies = function (types) {

        var results = {};
        var pending = [];

        for (var i = 0, il = types.length; i < il; i++) {

            var type = types[i];
            var value = this.getDependencies(type);

            // TODO: Error-prone use of a callback inside a loop.
            value = value.then(function (key, value) {

                results[key] = value;

            }.bind(this, type + (type === 'mesh' ? 'es' : 's')));

            pending.push(value);

        }

        return Promise.all(pending).then(function () {

            return results;

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferIndex
     * @return {Promise<ArrayBuffer>}
     */
    GLTFParser.prototype.loadBuffer = function (bufferIndex) {

        var bufferDef = this.json.buffers[bufferIndex];
        var loader = this.fileLoader;

        if (bufferDef.type && bufferDef.type !== 'arraybuffer') {

            throw new Error('THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.');

        }

        // If present, GLB container is required to be the first buffer.
        if (bufferDef.uri === undefined && bufferIndex === 0) {

            return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body);

        }

        var options = this.options;

        return new Promise(function (resolve, reject) {

            loader.load(resolveURL(bufferDef.uri, options.path), resolve, undefined, function () {

                reject(new Error('THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'));

            });

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferViewIndex
     * @return {Promise<ArrayBuffer>}
     */
    GLTFParser.prototype.loadBufferView = function (bufferViewIndex) {

        var bufferViewDef = this.json.bufferViews[bufferViewIndex];

        return this.getDependency('buffer', bufferViewDef.buffer).then(function (buffer) {

            var byteLength = bufferViewDef.byteLength || 0;
            var byteOffset = bufferViewDef.byteOffset || 0;
            return buffer.slice(byteOffset, byteOffset + byteLength);

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
     * @param {number} accessorIndex
     * @return {Promise<THREE.BufferAttribute|THREE.InterleavedBufferAttribute>}
     */
    GLTFParser.prototype.loadAccessor = function (accessorIndex) {

        var parser = this;
        var json = this.json;

        var accessorDef = this.json.accessors[accessorIndex];

        if (accessorDef.bufferView === undefined && accessorDef.sparse === undefined) {

            // Ignore empty accessors, which may be used to declare runtime
            // information about attributes coming from another source (e.g. Draco
            // compression extension).
            return Promise.resolve(null);

        }

        var pendingBufferViews = [];

        if (accessorDef.bufferView !== undefined) {

            pendingBufferViews.push(this.getDependency('bufferView', accessorDef.bufferView));

        } else {

            pendingBufferViews.push(null);

        }

        if (accessorDef.sparse !== undefined) {

            pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.indices.bufferView));
            pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.values.bufferView));

        }

        return Promise.all(pendingBufferViews).then(function (bufferViews) {

            var bufferView = bufferViews[0];

            var itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
            var TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

            // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
            var elementBytes = TypedArray.BYTES_PER_ELEMENT;
            var itemBytes = elementBytes * itemSize;
            var byteOffset = accessorDef.byteOffset || 0;
            var byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[accessorDef.bufferView].byteStride : undefined;
            var normalized = accessorDef.normalized === true;
            var array, bufferAttribute;

            // The buffer is not interleaved if the stride is the item size in bytes.
            if (byteStride && byteStride !== itemBytes) {

                var ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType;
                var ib = parser.cache.get(ibCacheKey);

                if (!ib) {

                    // Use the full buffer if it's interleaved.
                    array = new TypedArray(bufferView);

                    // Integer parameters to IB/IBA are in array elements, not bytes.
                    ib = new THREE.InterleavedBuffer(array, byteStride / elementBytes);

                    parser.cache.add(ibCacheKey, ib);

                }

                bufferAttribute = new THREE.InterleavedBufferAttribute(ib, itemSize, byteOffset / elementBytes, normalized);

            } else {

                if (bufferView === null) {

                    array = new TypedArray(accessorDef.count * itemSize);

                } else {

                    array = new TypedArray(bufferView, byteOffset, accessorDef.count * itemSize);

                }

                bufferAttribute = new THREE.BufferAttribute(array, itemSize, normalized);

            }

            // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
            if (accessorDef.sparse !== undefined) {

                var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
                var TypedArrayIndices = WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType];

                var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
                var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

                var sparseIndices = new TypedArrayIndices(bufferViews[1], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices);
                var sparseValues = new TypedArray(bufferViews[2], byteOffsetValues, accessorDef.sparse.count * itemSize);

                if (bufferView !== null) {

                    // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
                    bufferAttribute.setArray(bufferAttribute.array.slice());

                }

                for (var i = 0, il = sparseIndices.length; i < il; i++) {

                    var index = sparseIndices[i];

                    bufferAttribute.setX(index, sparseValues[i * itemSize]);
                    if (itemSize >= 2) bufferAttribute.setY(index, sparseValues[i * itemSize + 1]);
                    if (itemSize >= 3) bufferAttribute.setZ(index, sparseValues[i * itemSize + 2]);
                    if (itemSize >= 4) bufferAttribute.setW(index, sparseValues[i * itemSize + 3]);
                    if (itemSize >= 5) throw new Error('THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.');

                }

            }

            return bufferAttribute;

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
     * @param {number} textureIndex
     * @return {Promise<THREE.Texture>}
     */
    GLTFParser.prototype.loadTexture = function (textureIndex) {

        var parser = this;
        var json = this.json;
        var options = this.options;
        var textureLoader = this.textureLoader;

        var URL = window.URL || window.webkitURL;

        var textureDef = json.textures[textureIndex];

        var textureExtensions = textureDef.extensions || {};

        var source;

        if (textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]) {

            source = json.images[textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS].source];

        } else {

            source = json.images[textureDef.source];

        }

        var sourceURI = source.uri;
        var isObjectURL = false;

        if (source.bufferView !== undefined) {

            // Load binary image data from bufferView, if provided.

            sourceURI = parser.getDependency('bufferView', source.bufferView).then(function (bufferView) {

                isObjectURL = true;
                var blob = new Blob([bufferView], {
                    type: source.mimeType
                });
                sourceURI = URL.createObjectURL(blob);
                return sourceURI;

            });

        }

        return Promise.resolve(sourceURI).then(function (sourceURI) {

            // Load Texture resource.

            var loader = THREE.Loader.Handlers.get(sourceURI);

            if (!loader) {

                loader = textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS] ?
                    parser.extensions[EXTENSIONS.MSFT_TEXTURE_DDS].ddsLoader :
                    textureLoader;

            }

            return new Promise(function (resolve, reject) {

                loader.load(resolveURL(sourceURI, options.path), resolve, undefined, reject);

            });

        }).then(function (texture) {

            // Clean up resources and configure Texture.

            if (isObjectURL === true) {

                URL.revokeObjectURL(sourceURI);

            }

            texture.flipY = false;

            if (textureDef.name !== undefined) texture.name = textureDef.name;

            // Ignore unknown mime types, like DDS files.
            if (source.mimeType in MIME_TYPE_FORMATS) {

                texture.format = MIME_TYPE_FORMATS[source.mimeType];

            }

            var samplers = json.samplers || {};
            var sampler = samplers[textureDef.sampler] || {};

            texture.magFilter = WEBGL_FILTERS[sampler.magFilter] || THREE.LinearFilter;
            texture.minFilter = WEBGL_FILTERS[sampler.minFilter] || THREE.LinearMipMapLinearFilter;
            texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || THREE.RepeatWrapping;
            texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || THREE.RepeatWrapping;

            return texture;

        });

    };

    /**
     * Asynchronously assigns a texture to the given material parameters.
     * @param {Object} materialParams
     * @param {string} mapName
     * @param {Object} mapDef
     * @return {Promise}
     */
    GLTFParser.prototype.assignTexture = function (materialParams, mapName, mapDef) {

        var parser = this;

        return this.getDependency('texture', mapDef.index).then(function (texture) {

            switch (mapName) {

                case 'aoMap':
                case 'emissiveMap':
                case 'metalnessMap':
                case 'normalMap':
                case 'roughnessMap':
                    texture.format = THREE.RGBFormat;
                    break;

            }

            if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {

                var transform = mapDef.extensions !== undefined ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] : undefined;

                if (transform) {

                    texture = parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM].extendTexture(texture, transform);

                }

            }

            materialParams[mapName] = texture;

        });

    };

    /**
     * Assigns final material to a Mesh, Line, or Points instance. The instance
     * already has a material (generated from the glTF material options alone)
     * but reuse of the same glTF material may require multiple threejs materials
     * to accomodate different primitive types, defines, etc. New materials will
     * be created if necessary, and reused from a cache.
     * @param  {THREE.Object3D} mesh Mesh, Line, or Points instance.
     */
    GLTFParser.prototype.assignFinalMaterial = function (mesh) {

        var geometry = mesh.geometry;
        var material = mesh.material;
        var extensions = this.extensions;

        var useVertexTangents = geometry.attributes.tangent !== undefined;
        var useVertexColors = geometry.attributes.color !== undefined;
        var useFlatShading = geometry.attributes.normal === undefined;
        var useSkinning = mesh.isSkinnedMesh === true;
        var useMorphTargets = Object.keys(geometry.morphAttributes).length > 0;
        var useMorphNormals = useMorphTargets && geometry.morphAttributes.normal !== undefined;

        if (mesh.isPoints) {

            var cacheKey = 'PointsMaterial:' + material.uuid;

            var pointsMaterial = this.cache.get(cacheKey);

            if (!pointsMaterial) {

                pointsMaterial = new THREE.PointsMaterial();
                THREE.Material.prototype.copy.call(pointsMaterial, material);
                pointsMaterial.color.copy(material.color);
                pointsMaterial.map = material.map;
                pointsMaterial.lights = false; // PointsMaterial doesn't support lights yet

                this.cache.add(cacheKey, pointsMaterial);

            }

            material = pointsMaterial;

        } else if (mesh.isLine) {

            var cacheKey = 'LineBasicMaterial:' + material.uuid;

            var lineMaterial = this.cache.get(cacheKey);

            if (!lineMaterial) {

                lineMaterial = new THREE.LineBasicMaterial();
                THREE.Material.prototype.copy.call(lineMaterial, material);
                lineMaterial.color.copy(material.color);
                lineMaterial.lights = false; // LineBasicMaterial doesn't support lights yet

                this.cache.add(cacheKey, lineMaterial);

            }

            material = lineMaterial;

        }

        // Clone the material if it will be modified
        if (useVertexTangents || useVertexColors || useFlatShading || useSkinning || useMorphTargets) {

            var cacheKey = 'ClonedMaterial:' + material.uuid + ':';

            if (material.isGLTFSpecularGlossinessMaterial) cacheKey += 'specular-glossiness:';
            if (useSkinning) cacheKey += 'skinning:';
            if (useVertexTangents) cacheKey += 'vertex-tangents:';
            if (useVertexColors) cacheKey += 'vertex-colors:';
            if (useFlatShading) cacheKey += 'flat-shading:';
            if (useMorphTargets) cacheKey += 'morph-targets:';
            if (useMorphNormals) cacheKey += 'morph-normals:';

            var cachedMaterial = this.cache.get(cacheKey);

            if (!cachedMaterial) {

                cachedMaterial = material.isGLTFSpecularGlossinessMaterial ?
                    extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].cloneMaterial(material) :
                    material.clone();

                if (useSkinning) cachedMaterial.skinning = true;
                if (useVertexTangents) cachedMaterial.vertexTangents = true;
                if (useVertexColors) cachedMaterial.vertexColors = THREE.VertexColors;
                if (useFlatShading) cachedMaterial.flatShading = true;
                if (useMorphTargets) cachedMaterial.morphTargets = true;
                if (useMorphNormals) cachedMaterial.morphNormals = true;

                this.cache.add(cacheKey, cachedMaterial);

            }

            material = cachedMaterial;

        }

        // workarounds for mesh and geometry

        if (material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined) {

            console.log('THREE.GLTFLoader: Duplicating UVs to support aoMap.');
            geometry.addAttribute('uv2', new THREE.BufferAttribute(geometry.attributes.uv.array, 2));

        }

        if (material.isGLTFSpecularGlossinessMaterial) {

            // for GLTFSpecularGlossinessMaterial(ShaderMaterial) uniforms runtime update
            mesh.onBeforeRender = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].refreshUniforms;

        }

        mesh.material = material;

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
     * @param {number} materialIndex
     * @return {Promise<THREE.Material>}
     */
    GLTFParser.prototype.loadMaterial = function (materialIndex) {

        var parser = this;
        var json = this.json;
        var extensions = this.extensions;
        var materialDef = json.materials[materialIndex];

        var materialType;
        var materialParams = {};
        var materialExtensions = materialDef.extensions || {};

        var pending = [];

        if (materialExtensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]) {

            var sgExtension = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS];
            materialType = sgExtension.getMaterialType(materialDef);
            pending.push(sgExtension.extendParams(materialParams, materialDef, parser));

        } else if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {

            var kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT];
            materialType = kmuExtension.getMaterialType(materialDef);
            pending.push(kmuExtension.extendParams(materialParams, materialDef, parser));

        } else {

            // Specification:
            // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

            materialType = THREE.MeshStandardMaterial;

            var metallicRoughness = materialDef.pbrMetallicRoughness || {};

            materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
            materialParams.opacity = 1.0;

            if (Array.isArray(metallicRoughness.baseColorFactor)) {

                var array = metallicRoughness.baseColorFactor;

                materialParams.color.fromArray(array);
                materialParams.opacity = array[3];

            }

            if (metallicRoughness.baseColorTexture !== undefined) {

                pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));

            }

            materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
            materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;

            if (metallicRoughness.metallicRoughnessTexture !== undefined) {

                pending.push(parser.assignTexture(materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture));
                pending.push(parser.assignTexture(materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture));

            }

        }

        if (materialDef.doubleSided === true) {

            materialParams.side = THREE.DoubleSide;

        }

        var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

        if (alphaMode === ALPHA_MODES.BLEND) {

            materialParams.transparent = true;

        } else {

            materialParams.transparent = false;

            if (alphaMode === ALPHA_MODES.MASK) {

                materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;

            }

        }

        if (materialDef.normalTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

            pending.push(parser.assignTexture(materialParams, 'normalMap', materialDef.normalTexture));

            materialParams.normalScale = new THREE.Vector2(1, 1);

            if (materialDef.normalTexture.scale !== undefined) {

                materialParams.normalScale.set(materialDef.normalTexture.scale, materialDef.normalTexture.scale);

            }

        }

        if (materialDef.occlusionTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

            pending.push(parser.assignTexture(materialParams, 'aoMap', materialDef.occlusionTexture));

            if (materialDef.occlusionTexture.strength !== undefined) {

                materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;

            }

        }

        if (materialDef.emissiveFactor !== undefined && materialType !== THREE.MeshBasicMaterial) {

            materialParams.emissive = new THREE.Color().fromArray(materialDef.emissiveFactor);

        }

        if (materialDef.emissiveTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

            pending.push(parser.assignTexture(materialParams, 'emissiveMap', materialDef.emissiveTexture));

        }

        return Promise.all(pending).then(function () {

            var material;

            if (materialType === THREE.ShaderMaterial) {

                material = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].createMaterial(materialParams);

            } else {

                material = new materialType(materialParams);

            }

            if (materialDef.name !== undefined) material.name = materialDef.name;

            // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
            if (material.map) material.map.encoding = THREE.sRGBEncoding;
            if (material.emissiveMap) material.emissiveMap.encoding = THREE.sRGBEncoding;
            if (material.specularMap) material.specularMap.encoding = THREE.sRGBEncoding;

            assignExtrasToUserData(material, materialDef);

            if (materialDef.extensions) addUnknownExtensionsToUserData(extensions, material, materialDef);

            return material;

        });

    };

    /**
     * @param {THREE.BufferGeometry} geometry
     * @param {GLTF.Primitive} primitiveDef
     * @param {GLTFParser} parser
     * @return {Promise<THREE.BufferGeometry>}
     */
    function addPrimitiveAttributes(geometry, primitiveDef, parser) {

        var attributes = primitiveDef.attributes;

        var pending = [];

        function assignAttributeAccessor(accessorIndex, attributeName) {

            return parser.getDependency('accessor', accessorIndex)
                .then(function (accessor) {

                    geometry.addAttribute(attributeName, accessor);

                });

        }

        for (var gltfAttributeName in attributes) {

            var threeAttributeName = ATTRIBUTES[gltfAttributeName];

            if (!threeAttributeName) continue;

            // Skip attributes already provided by e.g. Draco extension.
            if (threeAttributeName in geometry.attributes) continue;

            pending.push(assignAttributeAccessor(attributes[gltfAttributeName], threeAttributeName));

        }

        if (primitiveDef.indices !== undefined && !geometry.index) {

            var accessor = parser.getDependency('accessor', primitiveDef.indices).then(function (accessor) {

                geometry.setIndex(accessor);

            });

            pending.push(accessor);

        }

        assignExtrasToUserData(geometry, primitiveDef);

        return Promise.all(pending).then(function () {

            return primitiveDef.targets !== undefined ?
                addMorphTargets(geometry, primitiveDef.targets, parser) :
                geometry;

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
     *
     * Creates BufferGeometries from primitives.
     *
     * @param {Array<GLTF.Primitive>} primitives
     * @return {Promise<Array<THREE.BufferGeometry>>}
     */
    GLTFParser.prototype.loadGeometries = function (primitives) {

        var parser = this;
        var extensions = this.extensions;
        var cache = this.primitiveCache;

        function createDracoPrimitive(primitive) {

            return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
                .decodePrimitive(primitive, parser)
                .then(function (geometry) {

                    return addPrimitiveAttributes(geometry, primitive, parser);

                });

        }

        var pending = [];

        for (var i = 0, il = primitives.length; i < il; i++) {

            var primitive = primitives[i];
            var cacheKey = createPrimitiveKey(primitive);

            // See if we've already created this geometry
            var cached = cache[cacheKey];

            if (cached) {

                // Use the cached geometry if it exists
                pending.push(cached.promise);

            } else {

                var geometryPromise;

                if (primitive.extensions && primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]) {

                    // Use DRACO geometry if available
                    geometryPromise = createDracoPrimitive(primitive);

                } else {

                    // Otherwise create a new geometry
                    geometryPromise = addPrimitiveAttributes(new THREE.BufferGeometry(), primitive, parser);

                }

                // Cache this geometry
                cache[cacheKey] = {
                    primitive: primitive,
                    promise: geometryPromise
                };

                pending.push(geometryPromise);

            }

        }

        return Promise.all(pending);

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
     * @param {number} meshIndex
     * @return {Promise<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
     */
    GLTFParser.prototype.loadMesh = function (meshIndex) {

        var parser = this;
        var json = this.json;
        var extensions = this.extensions;

        var meshDef = json.meshes[meshIndex];
        var primitives = meshDef.primitives;

        var pending = [];

        for (var i = 0, il = primitives.length; i < il; i++) {

            var material = primitives[i].material === undefined ?
                createDefaultMaterial() :
                this.getDependency('material', primitives[i].material);

            pending.push(material);

        }

        return Promise.all(pending).then(function (originalMaterials) {

            return parser.loadGeometries(primitives).then(function (geometries) {

                var meshes = [];

                for (var i = 0, il = geometries.length; i < il; i++) {

                    var geometry = geometries[i];
                    var primitive = primitives[i];

                    // 1. create Mesh

                    var mesh;

                    var material = originalMaterials[i];

                    if (primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
                        primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
                        primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
                        primitive.mode === undefined) {

                        // .isSkinnedMesh isn't in glTF spec. See .markDefs()
                        mesh = meshDef.isSkinnedMesh === true ?
                            new THREE.SkinnedMesh(geometry, material) :
                            new THREE.Mesh(geometry, material);

                        if (mesh.isSkinnedMesh === true) mesh.normalizeSkinWeights(); // #15319

                        if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {

                            mesh.drawMode = THREE.TriangleStripDrawMode;

                        } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {

                            mesh.drawMode = THREE.TriangleFanDrawMode;

                        }

                    } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {

                        mesh = new THREE.LineSegments(geometry, material);

                    } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {

                        mesh = new THREE.Line(geometry, material);

                    } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {

                        mesh = new THREE.LineLoop(geometry, material);

                    } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {

                        mesh = new THREE.Points(geometry, material);

                    } else {

                        throw new Error('THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode);

                    }

                    if (Object.keys(mesh.geometry.morphAttributes).length > 0) {

                        updateMorphTargets(mesh, meshDef);

                    }

                    mesh.name = meshDef.name || ('mesh_' + meshIndex);

                    if (geometries.length > 1) mesh.name += '_' + i;

                    assignExtrasToUserData(mesh, meshDef);

                    parser.assignFinalMaterial(mesh);

                    meshes.push(mesh);

                }

                if (meshes.length === 1) {

                    return meshes[0];

                }

                var group = new THREE.Group();

                for (var i = 0, il = meshes.length; i < il; i++) {

                    group.add(meshes[i]);

                }

                return group;

            });

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
     * @param {number} cameraIndex
     * @return {Promise<THREE.Camera>}
     */
    GLTFParser.prototype.loadCamera = function (cameraIndex) {

        var camera;
        var cameraDef = this.json.cameras[cameraIndex];
        var params = cameraDef[cameraDef.type];

        if (!params) {

            console.warn('THREE.GLTFLoader: Missing camera parameters.');
            return;

        }

        if (cameraDef.type === 'perspective') {

            camera = new THREE.PerspectiveCamera(THREE.Math.radToDeg(params.yfov), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6);

        } else if (cameraDef.type === 'orthographic') {

            camera = new THREE.OrthographicCamera(params.xmag / -2, params.xmag / 2, params.ymag / 2, params.ymag / -2, params.znear, params.zfar);

        }

        if (cameraDef.name !== undefined) camera.name = cameraDef.name;

        assignExtrasToUserData(camera, cameraDef);

        return Promise.resolve(camera);

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
     * @param {number} skinIndex
     * @return {Promise<Object>}
     */
    GLTFParser.prototype.loadSkin = function (skinIndex) {

        var skinDef = this.json.skins[skinIndex];

        var skinEntry = {
            joints: skinDef.joints
        };

        if (skinDef.inverseBindMatrices === undefined) {

            return Promise.resolve(skinEntry);

        }

        return this.getDependency('accessor', skinDef.inverseBindMatrices).then(function (accessor) {

            skinEntry.inverseBindMatrices = accessor;

            return skinEntry;

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
     * @param {number} animationIndex
     * @return {Promise<THREE.AnimationClip>}
     */
    GLTFParser.prototype.loadAnimation = function (animationIndex) {

        var json = this.json;

        var animationDef = json.animations[animationIndex];

        var pendingNodes = [];
        var pendingInputAccessors = [];
        var pendingOutputAccessors = [];
        var pendingSamplers = [];
        var pendingTargets = [];

        for (var i = 0, il = animationDef.channels.length; i < il; i++) {

            var channel = animationDef.channels[i];
            var sampler = animationDef.samplers[channel.sampler];
            var target = channel.target;
            var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
            var input = animationDef.parameters !== undefined ? animationDef.parameters[sampler.input] : sampler.input;
            var output = animationDef.parameters !== undefined ? animationDef.parameters[sampler.output] : sampler.output;

            pendingNodes.push(this.getDependency('node', name));
            pendingInputAccessors.push(this.getDependency('accessor', input));
            pendingOutputAccessors.push(this.getDependency('accessor', output));
            pendingSamplers.push(sampler);
            pendingTargets.push(target);

        }

        return Promise.all([

            Promise.all(pendingNodes),
            Promise.all(pendingInputAccessors),
            Promise.all(pendingOutputAccessors),
            Promise.all(pendingSamplers),
            Promise.all(pendingTargets)

        ]).then(function (dependencies) {

            var nodes = dependencies[0];
            var inputAccessors = dependencies[1];
            var outputAccessors = dependencies[2];
            var samplers = dependencies[3];
            var targets = dependencies[4];

            var tracks = [];

            for (var i = 0, il = nodes.length; i < il; i++) {

                var node = nodes[i];
                var inputAccessor = inputAccessors[i];
                var outputAccessor = outputAccessors[i];
                var sampler = samplers[i];
                var target = targets[i];

                if (node === undefined) continue;

                node.updateMatrix();
                node.matrixAutoUpdate = true;

                var TypedKeyframeTrack;

                switch (PATH_PROPERTIES[target.path]) {

                    case PATH_PROPERTIES.weights:

                        TypedKeyframeTrack = THREE.NumberKeyframeTrack;
                        break;

                    case PATH_PROPERTIES.rotation:

                        TypedKeyframeTrack = THREE.QuaternionKeyframeTrack;
                        break;

                    case PATH_PROPERTIES.position:
                    case PATH_PROPERTIES.scale:
                    default:

                        TypedKeyframeTrack = THREE.VectorKeyframeTrack;
                        break;

                }

                var targetName = node.name ? node.name : node.uuid;

                var interpolation = sampler.interpolation !== undefined ? INTERPOLATION[sampler.interpolation] : THREE.InterpolateLinear;

                var targetNames = [];

                if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {

                    // node can be THREE.Group here but
                    // PATH_PROPERTIES.weights(morphTargetInfluences) should be
                    // the property of a mesh object under group.

                    node.traverse(function (object) {

                        if (object.isMesh === true && object.morphTargetInfluences) {

                            targetNames.push(object.name ? object.name : object.uuid);

                        }

                    });

                } else {

                    targetNames.push(targetName);

                }

                // KeyframeTrack.optimize() will modify given 'times' and 'values'
                // buffers before creating a truncated copy to keep. Because buffers may
                // be reused by other tracks, make copies here.
                for (var j = 0, jl = targetNames.length; j < jl; j++) {

                    var track = new TypedKeyframeTrack(
                        targetNames[j] + '.' + PATH_PROPERTIES[target.path],
                        THREE.AnimationUtils.arraySlice(inputAccessor.array, 0),
                        THREE.AnimationUtils.arraySlice(outputAccessor.array, 0),
                        interpolation
                    );

                    // Here is the trick to enable custom interpolation.
                    // Overrides .createInterpolant in a factory method which creates custom interpolation.
                    if (sampler.interpolation === 'CUBICSPLINE') {

                        track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline(result) {

                            // A CUBICSPLINE keyframe in glTF has three output values for each input value,
                            // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
                            // must be divided by three to get the interpolant's sampleSize argument.

                            return new GLTFCubicSplineInterpolant(this.times, this.values, this.getValueSize() / 3, result);

                        };

                        // Workaround, provide an alternate way to know if the interpolant type is cubis spline to track.
                        // track.getInterpolation() doesn't return valid value for custom interpolant.
                        track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;

                    }

                    tracks.push(track);

                }

            }

            var name = animationDef.name !== undefined ? animationDef.name : 'animation_' + animationIndex;

            return new THREE.AnimationClip(name, undefined, tracks);

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
     * @param {number} nodeIndex
     * @return {Promise<THREE.Object3D>}
     */
    GLTFParser.prototype.loadNode = function (nodeIndex) {

        var json = this.json;
        var extensions = this.extensions;
        var parser = this;

        var meshReferences = json.meshReferences;
        var meshUses = json.meshUses;

        var nodeDef = json.nodes[nodeIndex];

        return (function () {

            // .isBone isn't in glTF spec. See .markDefs
            if (nodeDef.isBone === true) {

                return Promise.resolve(new THREE.Bone());

            } else if (nodeDef.mesh !== undefined) {

                return parser.getDependency('mesh', nodeDef.mesh).then(function (mesh) {

                    var node;

                    if (meshReferences[nodeDef.mesh] > 1) {

                        var instanceNum = meshUses[nodeDef.mesh]++;

                        node = mesh.clone();
                        node.name += '_instance_' + instanceNum;

                        // onBeforeRender copy for Specular-Glossiness
                        node.onBeforeRender = mesh.onBeforeRender;

                        for (var i = 0, il = node.children.length; i < il; i++) {

                            node.children[i].name += '_instance_' + instanceNum;
                            node.children[i].onBeforeRender = mesh.children[i].onBeforeRender;

                        }

                    } else {

                        node = mesh;

                    }

                    // if weights are provided on the node, override weights on the mesh.
                    if (nodeDef.weights !== undefined) {

                        node.traverse(function (o) {

                            if (!o.isMesh) return;

                            for (var i = 0, il = nodeDef.weights.length; i < il; i++) {

                                o.morphTargetInfluences[i] = nodeDef.weights[i];

                            }

                        });

                    }

                    return node;

                });

            } else if (nodeDef.camera !== undefined) {

                return parser.getDependency('camera', nodeDef.camera);

            } else if (nodeDef.extensions &&
                nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL] &&
                nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light !== undefined) {

                return parser.getDependency('light', nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light);

            } else {

                return Promise.resolve(new THREE.Object3D());

            }

        }()).then(function (node) {

            if (nodeDef.name !== undefined) {

                node.name = THREE.PropertyBinding.sanitizeNodeName(nodeDef.name);

            }

            assignExtrasToUserData(node, nodeDef);

            if (nodeDef.extensions) addUnknownExtensionsToUserData(extensions, node, nodeDef);

            if (nodeDef.matrix !== undefined) {

                var matrix = new THREE.Matrix4();
                matrix.fromArray(nodeDef.matrix);
                node.applyMatrix(matrix);

            } else {

                if (nodeDef.translation !== undefined) {

                    node.position.fromArray(nodeDef.translation);

                }

                if (nodeDef.rotation !== undefined) {

                    node.quaternion.fromArray(nodeDef.rotation);

                }

                if (nodeDef.scale !== undefined) {

                    node.scale.fromArray(nodeDef.scale);

                }

            }

            return node;

        });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
     * @param {number} sceneIndex
     * @return {Promise<THREE.Scene>}
     */
    GLTFParser.prototype.loadScene = function () {

        // scene node hierachy builder

        function buildNodeHierachy(nodeId, parentObject, json, parser) {

            var nodeDef = json.nodes[nodeId];

            return parser.getDependency('node', nodeId).then(function (node) {

                if (nodeDef.skin === undefined) return node;

                // build skeleton here as well

                var skinEntry;

                return parser.getDependency('skin', nodeDef.skin).then(function (skin) {

                    skinEntry = skin;

                    var pendingJoints = [];

                    for (var i = 0, il = skinEntry.joints.length; i < il; i++) {

                        pendingJoints.push(parser.getDependency('node', skinEntry.joints[i]));

                    }

                    return Promise.all(pendingJoints);

                }).then(function (jointNodes) {

                    var meshes = node.isGroup === true ? node.children : [node];

                    for (var i = 0, il = meshes.length; i < il; i++) {

                        var mesh = meshes[i];

                        var bones = [];
                        var boneInverses = [];

                        for (var j = 0, jl = jointNodes.length; j < jl; j++) {

                            var jointNode = jointNodes[j];

                            if (jointNode) {

                                bones.push(jointNode);

                                var mat = new THREE.Matrix4();

                                if (skinEntry.inverseBindMatrices !== undefined) {

                                    mat.fromArray(skinEntry.inverseBindMatrices.array, j * 16);

                                }

                                boneInverses.push(mat);

                            } else {

                                console.warn('THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[j]);

                            }

                        }

                        mesh.bind(new THREE.Skeleton(bones, boneInverses), mesh.matrixWorld);

                    }

                    return node;

                });

            }).then(function (node) {

                // build node hierachy

                parentObject.add(node);

                var pending = [];

                if (nodeDef.children) {

                    var children = nodeDef.children;

                    for (var i = 0, il = children.length; i < il; i++) {

                        var child = children[i];
                        pending.push(buildNodeHierachy(child, node, json, parser));

                    }

                }

                return Promise.all(pending);

            });

        }

        return function loadScene(sceneIndex) {

            var json = this.json;
            var extensions = this.extensions;
            var sceneDef = this.json.scenes[sceneIndex];
            var parser = this;

            var scene = new THREE.Scene();
            if (sceneDef.name !== undefined) scene.name = sceneDef.name;

            assignExtrasToUserData(scene, sceneDef);

            if (sceneDef.extensions) addUnknownExtensionsToUserData(extensions, scene, sceneDef);

            var nodeIds = sceneDef.nodes || [];

            var pending = [];

            for (var i = 0, il = nodeIds.length; i < il; i++) {

                pending.push(buildNodeHierachy(nodeIds[i], scene, json, parser));

            }

            return Promise.all(pending).then(function () {

                return scene;

            });

        };

    }();

    return GLTFLoader;

})();

